feat(ui): give every panel one scrollbar, select and slider skin

Every scrolling surface carries the kit's .ui-scroll, which
draws the thin themed scrollbar from --scroll-thumb and --scroll-track; the
Context panel and others drew the platform's light scrollbar because the
page declares no dark color-scheme. The per-panel scrollbar rules go; Cyber
sets the two tokens and Cockpit's HUD windows keep their accent tint.

Selects draw .gev-field's own chevron instead of the platform arrow, the
voice selects join .gev-field, number fields keep dark spinners, and the
Street Level range uses the shared slider in its green.

src/data/bhoteKoshiEmbeddedMedia.js

@@ -1054,7 +1054,7 @@ export function createBhoteKoshiEmbeddedMedia({
     leader.innerHTML =
       '<path pathLength="1" fill="none" stroke="rgba(147,213,228,.72)" stroke-width="1.5"/><circle r="4" fill="#6be8ff" stroke="#ffffff" stroke-width="1.5"/>';
     const player = documentRef.createElement('div');
-    player.className = 'bhote-embedded-callout-player';
+    player.className = 'bhote-embedded-callout-player ui-scroll';
     const footer = documentRef.createElement('footer');
     const title = documentRef.createElement('strong');
     title.textContent = bhoteEventText(

src/data/bhoteKoshiEmbeddedMedia.test.mjs

@@ -348,7 +348,7 @@ test('camera updates retain a preload until the visible player loads', () => {
   assert.equal(frame.parent, root, 'keep the preload while the visible player starts');
   const card = root.children.find(node => node.tag === 'section');
   const body = card.children.find(node => node.className === 'bhote-embedded-callout-body');
-  const player = body.children.find(node => node.className === 'bhote-embedded-callout-player');
+  const player = body.children.find(node => node.className.split(' ').includes('bhote-embedded-callout-player'));
   player.children.find(node => node.tag === 'iframe').dispatchEvent(new Event('load'));
   assert.equal(frame.parent, null, 'visible player readiness releases the preload');
   media.destroy();